Introduction
Pain after surgical procedures is a common feature, particularly in patients who have undergone general anesthesia, with approximately half of the individuals experiencing moderate to severe acute pain. The patient's immediate pain experience may be linked to their attitude, beliefs, and personality. Adequate postoperative administration of analgesia has been linked to fewer cardiopulmonary complications, reduced morbidity and mortality, reduced healthcare costs, and higher patient satisfaction. Standardizing multimodal analgesia with enhanced recovery after surgery (ERAS) is regarded as a healthcare quality improvement initiative. Acute pain which is not managed or poorly managed can result in complications and a longer rehabilitation period. Poor postoperative management is related to the onset of chronic pain and decreased quality of life.
Historically, opioid analgesic therapy has been the treatment of choice for acute postoperative pain. However, the recent increase in morbidity and mortality associated with the misuse of opioids has increased demand for more research into developing therapeutic pain approaches that place a greater emphasis on using a multimodal approach.
What Is the Pathophysiology of Acute Pain?
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A reaction to tissue injury causes acute pain due to tissue damage and injury to the small nerve fibers that occur during surgery. Afferent nociceptors, A-delta, and C-sensory fibers (Mechano-thermal and C-polymodal) are peripheral nerve endings with a high sensation for pain and activation threshold.
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As a result, noxious sensations generated by direct stimulation of A-delta and C-sensory fiber nerve endings and inflammation caused by a surgical incision will cause peripheral sensitization, increasing the sensitivity of these nociceptors. Transduction, transmission, perception, and modulation are the four processes that represent nociception.
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Substance P, histamine, bradykinins, prostaglandins, serotonin, and other mediators released by damaged cells induce nociceptors (transduction) to send afferent impulses to the spinal cord through the dorsal root ganglion (transmission).
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Finally, the midbrain's activation causes neurotransmitters such as endorphins, serotonin, enkephalin, and dynorphin, which descend to the lower central nervous system.
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Endogenous opioids are released when these neurotransmitters are activated. Opioid receptors are synthesized or upregulated in sensory neurons acting centrally and peripherally. Endogenous opioids bind to these receptors and decrease excitability. Immunocompetent cells appear to release opioid peptides from the periphery.
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Opioid receptors will function as presynaptic receptors in the brain. Opioid peptides are released by interneurons in the dorsal horn, resulting in pain transmission inhibition (modulation).
What Are the Ways to Assess Pain?
It is preferable to assess the pain before administering analgesics to determine the severity of the pain.
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Numeric Rating Scale (NRS):
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It is the most commonly used pain assessment scale because it is simple to employ and extensively used for research purposes. The patient is asked to choose a number ranging from zero to ten that best represents the intensity of their pain. Zero represents no pain, and ten represents the most severe pain.
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It is further classified for the purpose of intervention. Zero indicates no pain, one to three indicates mild pain, four to six indicates moderate pain, and seven to ten indicates severe pain. The numeric rating scale (NRS) can be given verbally over the phone or graphically for self-completion.
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Visual Analog Scale (VAS):
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The visual analog scale (VAS) has a sensory component and is regarded as a reliable pain measurement. The score is determined by measuring the distance (millimeters) on the ten-centimeter line between the "no pain" and the patient's mark, providing a range of scores from zero to hundred.
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As with the NRS, categories can be imposed (no pain 0 to 4 millimeters, mild pain 5 to 44 millimeters, moderate pain 45 to 74 millimeters, and severe pain 75 to 100 millimeters), but these are arbitrary scores.
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What Are the Management Strategies for Pain Management?
For reducing and managing postoperative pain, many preoperative, intraoperative, and postoperative interventions and management methods are available and are constantly evolving. The following treatments are used in the multimodal treatment of pain in postsurgical patients:
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Systemic Pharmacologic Therapy:
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Opioids, non-steroidal anti-inflammatory drugs (NSAIDs) and Acetaminophen, Steroids, Gabapentin or Pregabalin, IV (intravenous) Ketamine, and IV Lidocaine are all commonly used drugs for postoperative pain management.
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Opioid medication should be taken orally rather than intravenously. Intramuscular medications are not recommended. However, when a parenteral route of administration is required (for example, risk of aspiration, painful obstruction of the ileus), intravenous patient-controlled analgesia (PCA) is advised.
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In opioid-naive patients receiving patient-controlled analgesia, it is important to prevent a basal infusion of opioid medication. Acetaminophen or NSAIDs are associated with lower opioid usage and better pain control than opioids alone.
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Gabapentin or Pregabalin are advised for use before surgery, particularly in opioid-tolerant patients, because they have been demonstrated to reduce opioid requirements. Ketamine is only used for serious conditions due to its wide - range of side effects.
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Local, Intra-Articular, or Topical Techniques:
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To enable the patient with site-specific pain control, peripheral nerve blocks, intra-articular anesthetic injections, wound infiltration with anesthetics, and topical anesthetics can be used. These methods are not generally used. Their application should be based on beneficial findings.
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Regional Anesthetic Techniques:
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Based on the technique, a local anesthetic with or without the addition of intravenous opioid drugs is an alternative for fascial plane block, site-specific regional anesthetic injections, or in certain cases, epidural injections.
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These procedures are typically performed under ultrasound guidance by an anesthesiologist. In instances where the duration of postoperative pain is prolonged, continuous intravenous medication (in drip form) is advisable over single-injection techniques.
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There is little data to indicate that intrapleural analgesia is beneficial, and high systemic absorption inside the pleural space increases the likelihood of drug toxicity.
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Neuraxial Anesthetic Techniques:
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An epidural injection with local anesthetic is usually used, with or without the addition of intravenous opioids. Opioid medications may also be injected intrathecally (spinally). Continuous infusion or patient-controlled analgesia are both possibilities for epidural analgesia.
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These techniques are intended to be used routinely in major thoracic and abdominal procedures, cesarean sections, and hip or lower extremity surgeries.
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They are particularly useful in patients at risk of pulmonary or cardiac complications and prolonged, painful obstruction of the ileus.
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Nonpharmacologic Therapies: Nonpharmacologic pain management therapies include cognitive and mechanical modalities such as transcutaneous electrical nerve stimulation.
Conclusion
Postoperative pain management is an intricate task requiring teamwork from the preoperative setting through patient recovery. Compared to dependence on opioid therapy, a multimodal, interprofessional approach to pain control enables safer, more effective pain relief in the postoperative period. Inadequate postoperative pain control can have negative physiologic effects in the early postoperative period and raises the possibility of developing a chronic pain syndrome. Moreover, it has been demonstrated that optimized postoperative pain control reduces patient suffering, reduces hospital length of stay, aids in earlier mobilization and capacity to perform daily activities, and enhances patient satisfaction.
